The present invention concerns a system and a method for reading coded information.
Specifically, the present invention concerns a system and a method for reading coded information from an object.
The term “coded information” is used to indicate the set of identification data contained within a code, preferably an optical code. The term “optical code” is meant to indicate any graphical representation that has the function of storing said coded information. The term “optical code” comprise graphical representations detectable both in the visible light field and in the range of wavelengths between infrared and ultraviolet.
Particular examples of an optical code consist in linear or two-dimensional codes, in which information is encoded by using appropriate combinations of fixed shape elements, for example square, rectangular or hexagonal, of a dark color (usually black) separated by light elements (spaces, usually white), such as bar codes, stacked codes and two-dimensional codes in general, color codes, etc. The expression “optical code” also comprises, more generally, other graphical forms with an information coding function, including clearly printed characters (letters, numbers, etc.) and special patterns (“pattern”) (such as stamps, logos, signatures, fingerprints, etc.).
The coded information can relate, for example, to distance, volume, size, and/or identifying data of an object.
In transport and logistics commonly used systems are those of transport and the sorting of parcels, bags and more generally objects. With these systems, the objects are placed on a moving conveyor belt and identified on the basis of reading an optical code printed on a label associated with each object. Reading the optical code is performed automatically by means of a special automated coded information reading system.
As described by EP2681138, in the past, when there were only linear codes, optical code reading was performed by means of scanning an optical code using a beam of laser light emitted from a laser reader. With the advent of two-dimensional codes, the use of digital cameras has spread, typically utilizing CCD/CMOS sensors. These cameras allow greater flexibility of use; they are in fact able to read traditional linear codes two-dimensional codes and other types of codes, as well as offering additional features such as OCR (optical character recognition).
The Applicant has observed that the digital cameras used in these systems are two-dimensional (2D) cameras. The use of 2D cameras is however affected by problems of perspective distortion of the image due to the fact that a 2D system is being used to capture an object that in reality, is three-dimensional (3D). The elimination of this distortion from the captured 2D images requires the use of complex correction algorithms.
In addition, to ensure the identification of coded information that may be present on a face of any object, these systems require the use of multiple 2D cameras. The Applicant has, however, observed that, in order to ensure the detection of an optical code in every possible situation, it is necessary to over-specify the number of cameras in such a way as to ensure that there is at least one camera that can capture all of the optical code in its entirety, even in the most unfavorable of cases (namely, an optical code located near the camera and/or an optical code of maximum dimensions). In addition, in the case of objects that are very close to one another along the direction of travel of the conveyor belt and/or along a direction that is perpendicular to it, there is the problem of distinguishing those objects in order to make a correct association between the optical code and a respective object. As is evident from EP2681138, avoiding this problem requires the use of additional equipment and/or complicated algorithms and often results in decreased guaranteed reading performance due to the intrinsic limitations of the solution implemented (it requires the customer to keep objects spaced far apart, to reduce the speed of movement, to reduce the maximum dimensions and/or to increase the minimum dimensions of the objects being processed, etc).
The Applicant has therefore raised the technical problem of providing a system and an improved method for reading coded information compared to those of the prior art.
In particular, the Applicant has raised the technical problem of providing a system and a method for reading coded information that allows the above mentioned problems relating to the perspective distortion of the image, the over-specifying of the cameras and the distinguishing of objects that are very close to one another to be eliminated, both along the direction of travel of the conveyor belt and along a direction perpendicular to it.
The Applicant has found that this technical problem can be solved through the use of one or more three-dimensional cameras, designed to capture three-dimensional images of the object, and appropriate processing of the captured three-dimensional images that is designed to generate two-dimensional images of the object upon which to implement coded information recognition algorithms; the processing of the images comprising an operation of identifying planes upon which faces of the object lie (namely, faces that delimit the volume of the object) and an operation for extracting two-dimensional images that lie on the identified planes.
The Applicant has, in fact, perceived that obtaining two-dimensional images of the object from three-dimensional images allows two-dimensional images to be obtained that already lack any perspective distortion. Also, given that the three-dimensional images already carry information regarding the volume of the object, it is possible, thanks to the operation of identifying planes upon which faces of the object lie, to distinguish—from the beginning—one object from another, being ensured that the two-dimensional images that are obtained from said processing of the 3D images relate to one and only one object (and therefore only contain coded information belonging to that object). In other words, the problem of having to correctly associate an optical code with each object is eliminated at source. The two-dimensional images obtained using the methodology of the invention are thus already representative of the faces of interest of an object without redundancy and without perspective distortion. This represents notable technical progress with respect to the prior art described above.
Furthermore, with the use of three-dimensional cameras, it is no longer necessary to over specify the number of cameras as described above. In fact, in cases where the coded information can be located on any face of an object, overlapping is only required in order to guarantee capturing—with the plurality of three-dimensional cameras—the entire volume of the object, without discontinuity, and it is no longer linked to the characteristics of the application: minimum and maximum dimensions of the objects and optical codes that must be recognized. Furthermore, in applications where the presence of coded information is limited to a predetermined subset of faces of an object (for example, 1, 2 or 3 predetermined faces), it may be sufficient to use a single three-dimensional camera.
What is more, it is possible to obtain information regarding the shape and/or volume of an object, without requiring additional equipment (such as a volume sensor).
Finally, given that the coded information recognition algorithms are performed with two-dimensional images, algorithms that are well-known in the art can advantageously be used, acting upon two-dimensional images.